This study emphasizes the importance of timely and accurate information on the increase in gun crimes, and aims to develop an inexpensive gun detection and classification system that utilizes acoustic analysis of common devices such as smartphones as an alternative to expensive commercial gun detection systems. Using a dataset of 3,459 gun sound recordings, we analyzed acoustic features (muzzle blast and shock wave) by gun type, and evaluated the performance of gun detection and classification using SVM and CNN-based machine learning models. As a result, we confirmed that the CNN model showed better performance (mAP 0.58 vs. 0.39) than the SVM model, but the performance deteriorated (mAP 0.35) when using web data containing noise. Ultimately, we aim to develop an accurate and real-time system that operates on common recording devices to provide important information to first responders.